Minnows galore! sampling for an invasive species in northern Sweden

Invasive species can cause detrimental socioeconomic and environmental effects on the areas they invade. These can include modifications to habitats and food web structure manifested by competition with native species for resources. While there are many drivers of invasions, many of these are anthropogenic (the aquarium trade and ballast waters, for example). Natural resource agencies spend millions of dollars on invasive species mitigation efforts to prevent or mitigate their effects on important resources, such as managed fishery species.

The European/Eurasian minnow (hereafter minnow) is among the invasive species that have colonized widespread habitats across many latitudes. They have been documented to reduce the abundance of benthic organisms (such as aquatic insects) through predation and to modify the growth rates and diets of native salmonids (such as Arctic char [Salvelinus alpinus] and brown trout [Salmo trutta]) through competition. The latter is additionally concerning, as many salmonids support fisheries, and the minnow-induced effects on these species can reduce stakeholder satisfaction.

For my LOREX project, I documented the presence of minnows across the Torneträsk catchment in northern Sweden. I sampled lakes across a climatic and altitudinal gradient using minnow traps. This consisted of hiking through many types of terrain and changes in elevation to reach these lakes! I wouldn’t have been able to do this without the help of my fellow LOREXers, Antrelle Clark and Dr. Sara Wang! We called ourselves the Minnows and Benthos Crew!

The Minnows and Benthos crew out in the wild!

Minnows were retained to collect information on their population demographics and resource use. Specifically, we recorded lengths, weights, and sex, and collected otoliths (ear stones) for aging purposes, gonads for fecundity analysis, guts for stomach content analysis, and muscle tissue for both stable isotope and mercury analyses. The stable isotope analysis will allow us to make inferences about resource use, while the mercury analysis will allow us to investigate mercury concentrations in the species across the catchment.

Clockwise from top left: European/Eurasian minnow (Phoxinus phoxinus), European bullhead (Cottus gobio), burbot (Lota lota), and brown trout (Salmo trutta)

We have concluded fieldwork and fish processing in a very truncated amount of time. We sampled over 30 lakes and collected 449 minnows! I have conducted first reads on all collected otoliths, and the preliminary maximum age observed is 9 years! I have also developed length-weight relationships and growth models for minnows in the region. We also documented parasites in the stomachs of multiple minnows! More is yet to come. Up next, we will conduct stomach content analysis and send off muscle samples for stable isotope analysis. In unison, all this information will provide insights into the minnow population and their impacts on the local fauna and food web dynamics. This information will be very useful to resource managers, as there has already been documentation on the impacts of minnows on native salmonid species that support socioeconomically important fisheries. We aim to make this information available to the public by publishing it in a peer-reviewed scientific journal.

Some of the views from the trip

It’s been a wonderful experience spending the summer in Sweden. I have experienced cultural immersion, conducted meaningful research in the Arctic, and made new friends and colleagues. This experience has provided so much personal and professional growth. I’d like to take this moment to express my profound gratitude to the LOREX program! I feel deeply indebted to the program for everything it has provided me. I would also like to acknowledge and thank my collaborator, Dr. Pär Byström (Umeå University), for his willingness to work with me on this project and for providing technical and financial support. Part of a graduate student’s program (in my opinion) is to expose oneself to as many experiences as possible. Not that you should just be a “yes” person, but always try to take up as many experiences as possible, assuming time allows for it. During my doctoral program, I’ve been lucky enough to visit multiple countries, primarily by looking for opportunities and applying, such as the LOREX program. These visits weren’t even directly related to my dissertation research (I feel like my LOREX project could easily be a solid master’s thesis). You never know what new opportunities may bring you… new colleagues, professional opportunities, and/or personal relationships. If you find yourself considering applying for an international research program, such as LOREX, strongly consider it. Reach out to program alumni or colleagues who have conducted international research. You’ll have so much to potentially gain with little to lose.